JP3252834B2 - Exposure apparatus and exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for transferring a circuit pattern of a semiconductor device or the like.

[0002]

2. Description of the Related Art Conventionally, this type of apparatus has a configuration as shown in FIG. FIG. 4 is a diagram showing a schematic configuration from the Fourier transform surface of a reticle to a wafer of a projection type exposure apparatus in the related art. The light beam (exposure light) illuminating the reticle 18 is a light beam having an intensity distribution centered on the optical axis (AX) on the Fourier transform surface (position of the aperture stop in the illumination optical system) 12. Light is incident at a certain angle centered on the vertical direction. Here, only a light beam passing through a point on the optical axis AX in the Fourier plane 12 will be considered. This light beam is diffracted by the circuit pattern 19 on the reticle, and the 0th-order diffracted light Do, the + 1st-order diffracted light Dp, -1
Next-order diffracted light Dm is generated. At this time, the angle θ between the diffracted lights Do and Dp is equal to the angle θ between the diffracted lights Do and Dm, and
The pitch of the circuit pattern 19 is P, and the wavelength of the exposure light is λ.
Then, the diffraction angle θ is determined by sin θ = λ / P. The value of this sin θ is the object side of the projection optical system 20 (the reticle 18
Side), the zero-order diffracted light Do
The ± first-order diffracted light Dp passes through the projection optical system 20, condenses and interferes on the wafer 22, and forms an image of the circuit pattern 19.

Recently, in order to reduce the minimum pitch (line width) of a circuit pattern resolvable on a wafer, a phase shift reticle disclosed in Japanese Patent Publication No. 63-50811 may be used. Proposed.

[0004]

However, in the prior art as described above, when the pitch P of the circuit pattern is reduced, the value of sin θ increases, and finally the numerical aperture NA _M on the reticle side of the projection optical system. It will be larger. Then, the ± 1st-order diffracted lights Dp and Dm can no longer pass through the projection optical system 20, and the light flux reaching the wafer 22 is only the 0th-order diffracted light Do. Even if only the zero-order diffracted light reaches the wafer, no interference fringes are generated, and it is impossible to form an image of the circuit pattern. That is, in conventional exposure apparatus, the pitch P given by P = lambda / NA _M was the smallest of the reticle on the pattern size to be transferred to the wafer.

[0005] Even when a phase shift reticle is used, it has been difficult to manufacture and inspect the phase shift reticle.

[0006]

An exposure apparatus according to the present invention comprises an illumination optical system (1) for irradiating a mask (18) with illumination light.
17) and a projection optical system (20) for projecting illumination light onto the substrate (22), and transfers the mask pattern (19) onto the substrate. Then, the illumination light (L5) is respectively set at a plurality of positions decentered from the optical axis (AX) on the pupil plane (12) of the illumination optical system such that the illumination light (L5) is incident on the mask at a predetermined incident angle from different directions. A movable optical member (9; 9a, 9b; 9c) for setting an intensity center; and a drive for driving the movable optical member such that when the pattern is transferred onto the substrate, the intensity center of the illumination light can be switched to a plurality of positions. The members (10a, 10b; 10c, 10d; 10e) are provided.

Further, according to the exposure method of the present invention, the mask (18) is irradiated with illumination light through the illumination optical systems (1 to 17), and the substrate (22) is irradiated with the illumination light through the projection optical system (20). Exposure. Then, the movable optical member (9; 9a, 9a, 9a,
9b), the intensity center of the illumination light is switched and set to a plurality of positions decentered from the optical axis (AX) on the pupil plane (12) of the illumination optical system, and the illumination is respectively performed at the plurality of positions. When the exposure amount given to the substrate by setting the light intensity center reaches a predetermined value, the irradiation of the illumination light onto the mask is terminated.

Further, the plurality of positions for setting the intensity center of the illumination light are separated from the optical axis in the pattern arrangement direction on the pupil plane of the illumination optical system, and the distance from the optical axis is changed according to the fineness of the pattern. Set almost equal. When the pattern has a periodic structure arranged at a first pitch in the first direction, the plurality of positions are positioned on the pupil plane of the illumination optical system from the optical axis in the first direction.
The direction is set on a pair of parallel first line segments (Lα, Lβ) separated by a distance corresponding to the first pitch in the directions. At this time, the distance between each first line segment and the optical axis is set such that the wavelength of the illumination light is λ and the first pitch is P, and the incident angle 照明 of the illumination light is sinψ = λ / 2P.

In the present invention, the pattern of the mask is first.
When a periodic structure is arranged at a first pitch (Px) in the direction and arranged at a second pitch (Py) in a second direction orthogonal to the first direction, the plurality of positions are determined by a pupil plane of the illumination optical system. A pair of parallel first line segments separated from the optical axis in the first direction by a distance corresponding to the first pitch, and a distance from the optical axis of the illumination optical system in the second direction by a distance corresponding to the second pitch. The point of intersection (L
γ, Lε, Lζ, Lη).

In the present invention, the movable optical members (9; 9a, 9b; 9c) are moved in the illumination optical system so that the illumination light (L5) is incident on the mask at a predetermined incident angle from different directions. The intensity center of the illumination light is switched and set to a plurality of positions decentered from the optical axis (AX) on the pupil plane (12) of the illumination optical system. For this reason, the illumination light can be incident from a direction inclined (the principal ray is not perpendicular) to the mask (the optical axis of the illumination optical system or the projection optical system), and the direction can be made variable. . Therefore, it is possible to transfer the pattern of the mask onto the substrate with high resolution.

Further, the pupil plane of the illumination optical system is such that the 0th-order diffracted light and the 1st-order diffracted light generated by the mask pass through the pupil plane of the projection optical system at a position substantially equidistant from the optical axis of the projection optical system. In order to determine the positions of the plurality of regions above, the wavefront aberration of the 0th-order diffracted light and the wavefront aberration of the 1st-order diffracted light due to the defocus of the pattern image of the mask projected on the substrate (wafer) are made substantially equal. Can be. Therefore, it is possible to transfer the mask pattern image onto the substrate with a large depth of focus.

[0012]

FIG. 1 is a diagram showing a schematic configuration of a projection type exposure apparatus according to a first embodiment of the present invention. The light beam L1 emitted from the light source 1 is transmitted through the elliptical mirror 2 to the lens system 5
Is irradiated. The light beam L1 is formed into a substantially parallel light beam L2 by the lens system 5, becomes a light beam L3 via the fly-eye lens 6 and the aperture stop 7, and is irradiated to the reflecting mirror 9 via the lens system 8. The light beam L4 reflected by the reflecting mirror 9 is applied to the field stop 14 via the lens systems 11 and 13. The field stop 14 is for determining the irradiation range of the illumination light on the reticle 18. Further, the light beam L5 that has passed through the field stop 14 is applied to a semi-transmissive mirror 16 via a lens system 15. The light beam L5 reflected by the semi-transmissive mirror 16 is irradiated on the reticle 18 at a predetermined incident angle via a lens system (main condenser lens) 17, and generates diffracted lights Do and Dp in a pattern 19 on the reticle 18. The diffracted lights Do and Dp generated by the pattern 19 form a projected image of the circuit pattern 19 on the wafer 22 via the projection optical system 20. The wafer 22 is held on a wafer stage 23. The wafer stage 23 moves in the optical axis AX direction of the projection optical system 20 for focusing, a tilt mechanism for tilting the wafer 22, and moves in a plane orthogonal to the optical axis AX for changing an exposure area. It has a mechanism and the like. On the other hand, the light beam transmitted through the semi-transmissive mirror 16 is condensed by a lens system 24 and is photoelectrically converted by a light amount measuring device 25 such as a semiconductor sensor. Light intensity meter 2
The light amount signal S obtained from 5 is transmitted to the control circuit 26 as an electric signal. The control circuit 26 gives an operation command to the shutter driving unit 4 for driving the shutter 3 and the driving elements 10a and 10b for driving the reflecting mirror 9 based on the light amount signal S. When the shutter drive unit 4 operates, the light beam L2 is blocked by the shutter 3, and the exposure is stopped. In the present embodiment, the shutter driving unit 4 and the driving elements 10a and 10b are controlled using the light amount measuring device 25. However, the light amount measuring device 25 is not provided, and the control is performed simply by the exposure time. Even so, the effect of the present invention does not change.

In the above configuration, the fly-eye lens 6
, The reflecting mirror 9, the field stop 14, the pattern surface 19 of the reticle 18, and the wafer 22 are conjugate with each other, and the exit surface of the fly-eye lens 6, the Fourier transform surface 12 of the reticle 18, and the projection optical system. The 20 pupil planes 21 are conjugate to each other. Fly-eye lens 6 is reticle 1
It is provided for the purpose of equalizing the illuminance on the eight surfaces, and the presence or absence of the fly-eye lens 6 does not directly affect the effect of the present invention. In order to make the illuminance uniform on the surface of the reticle 18, the incident surface of the fly-eye lens 6 is located at a position that forms an image with the reticle 18. On the other hand, the exit surface of the fly-eye lens is a position corresponding to the pupil plane when the pattern plane of the reticle 18 is the object plane. Therefore, by providing the aperture stop 7 at this position, the numerical aperture of the illumination light beam can be made variable.

The reflecting mirror 9 is located at a position substantially conjugate with the reticle 18 as described above, and is rotatable about, for example, two axes orthogonal to each other on a reflecting surface. The rotation of the reflecting mirror 9 is controlled by a driving element 10 such as a motor or a piezo element.
a, 10b. Although the reflected light L4 traveling in the direction of the light beam L4a is shown by a solid line in FIG. 1, by changing the rotation angle of the reflecting mirror 9, the reflected light beam L4a can be advanced in the direction of the light beam L4b, for example. That is, one secondary light source image at the exit end of the fly-eye lens 6 is
It shifts by two. Further, it is of course possible to have a moving component in a direction perpendicular to the paper surface of FIG.

In this embodiment, in order to move the reflecting mirror 9 as a movable optical member at a position substantially conjugate with the reticle 18, if the field stop 14 is closer to the light source than the reflecting mirror 9, the reflecting mirror 9 is moved. It is conceivable that the positional relationship between the reticle 18 and the field stop 14 is slightly displaced with the movement of. Therefore, it is desirable that the field stop 14 be closer to the reticle 18 than the reflecting mirror 9.

As a light source in this embodiment, a bright line lamp such as a mercury lamp or a laser can be used. In the case of a laser light source, the shutter 3 is omitted and the shutter driving unit 4
Instead, a mechanism for controlling the laser power supply (trigger for oscillation) may be provided. When the chromatic aberration of the optical elements in the projection optical system 20 and the illumination optical system (from the light source 1 to the lens system 17 in the figure) is not sufficiently corrected, for example, a band-pass filter or the like is included in the light beam L2 during the illumination constraint. What is necessary is just to use a wavelength selection element. Alternatively, a reflective member such as the elliptical mirror 2 may be used as a multilayer dielectric mirror to increase the reflectance only at a specific wavelength.

When a circuit pattern is transferred by the projection type exposure apparatus of this embodiment, the ratio between the numerical aperture of the illumination light beam and the numerical aperture on the photomask side of the projection optical system, that is, the so-called coherence factor σ is set to 0.1. About 2 to 0.3 is preferable. Therefore, the fly-eye lens 6 and the aperture stop 7 have σ =
It is set to be 0.2 to 0.3. In the exposure apparatus having the above configuration, the reflecting mirror 9 is connected to the driving elements 10a and 10a.
Drive at b to set at a predetermined position. Then, the light beam L4 whose principal ray is coaxial with the optical axis AX of the illumination optical system becomes an optical axis AX
The light beams L4a and L4b have chief rays inclined with respect to. The light beams L4a and L4b are condensed at positions different from the optical axis AX in the vicinity of the Fourier transform surface 12 of the reticle 18, respectively.

Therefore, the light beam L5 irradiated on the reticle 18 is obliquely incident on the reticle 18. By appropriately setting the incident angle of the light beam L5 to the reticle 18, the circuit pattern 19 on the reticle 18
The 0th-order diffracted light Do and the + 1st-order diffracted light Dp (or the 0th-order diffracted light Do and the -1st-order diffracted light Dm) generated by the projection optical system 2
The light is condensed by 0 and forms an interference fringe, that is, an image of the circuit pattern 19 on the wafer 22.

Here, the reason why the image of the circuit pattern 19 is formed on the wafer 22 by the diffracted lights Do and Dp will be described. FIG. 3 is a diagram showing a schematic configuration from the Fourier transform surface 12 of the reticle 18 to the wafer 22 of the projection type exposure apparatus according to the embodiment of the present invention. In FIG. 3, some of the optical elements in FIG. 1 are omitted for simplification.
There is no difference that 2 is the Fourier transform surface of the reticle 18.

In FIG. 3, L5a is a light beam having a center of intensity at a position shifted to the right from the optical axis on the Fourier transform surface 12, and is incident on the reticle 18 by the lens system 17 at a predetermined incident angle ψ. Accordingly, the zero-order diffracted light Do generated from the circuit pattern 19 on the reticle 18 is also generated in the direction of the angle に 対 し て with respect to the reticle 18. In directions away from the 0th-order diffracted light Do by angles θp and θm, respectively,
A + 1st-order diffracted light Dp and a -1st-order diffracted light Dm are generated. At this time, the angles θp and θm are respectively sinψ + sin (θp−ψ) = λ / P (1) sin (θm + ψ) −sinψ = λ / P (2) (where λ is the wavelength of the exposure light, P Is given by the pitch of the circuit pattern).

When the pitch P of the circuit pattern 19 becomes finer, θp and θm increase as in the prior art, and as shown in FIG.
The first-order diffracted light Dm cannot pass through the projection optical system 20.
However, since the light beam L5a is incident on the reticle 18 at an appropriate incident angle ψ, the + 1st-order diffracted lights Dp and 0
The next-order diffracted light Do can pass through the projection optical system 20 and reach the wafer 22. Therefore, an interference fringe due to the interference of the two light beams, that is, an image of the circuit pattern 19 is formed on the wafer 22. The interference fringe between the 0th-order diffracted light Do and the + 1st-order diffracted light Dp has an image contrast of 90.000 when the circuit pattern 19 on the reticle 18 is a so-called 1: 1 line and space. It is about 6%, which is sufficient contrast for patterning the resist applied on the wafer.

When the light beam L5a is incident on the reticle 18 at an incident angle も, the 0th-order diffracted light Do also exits at an angle 、, but the + 1st-order diffracted light Dp and the -1st-order diffracted light Dm respectively correspond to the optical axis AX. Inject at an angle of θp−ψ, θm + ψ. Even if the pitch P of the circuit pattern 19 is finer, focusing on the + 1st-order diffracted light Dp that can pass through the projection optical system 20 among the ± 1st-order diffracted lights, sin (θp−ψ) ≦
With the NA _M , the light can pass through the projection optical system 20 and the circuit pattern 19 can be imaged on the wafer.

From equation (1), sin (θp−ψ) = λ / P−sinψ ≦ NA _M λ / P ≦ NA _M + sinψ That is, for an incident angle ψ of the light beam, P ≧ λ / (NA _M + sinψ). The pitch P given by (3) is the reticle 18 in the present invention.
This is the minimum pitch at which the upper circuit pattern 19 can be transferred.

[0024] Now, it is assumed that the sinψ = 0.5 × NA _M. That is, the illumination light beam L5a is irradiated such that the principal ray passes through the outermost periphery of the pupil plane 21 of the projection optical system 20 and the midpoint between the optical axis AX. In this case, the pitch P which is obtained from equation (3) becomes _{P = λ / (NA M +} 0.5NA M) = 2λ / 3NA M.

On the other hand, in the conventional projection exposure apparatus, the pitch of the transferable minimum pattern is a P ≒ λ / NA _M.
Therefore, the minimum pitch of the circuit pattern that can be transferred by the projection exposure apparatus according to the embodiment of the present invention can be made finer than in the conventional case. In other words, a projection type exposure apparatus with higher resolution can be realized. However, the illumination light beam L5a for illuminating the reticle 18 is always
Assuming that the light beam L5a is incident on the wafer 22 at a constant incident angle, the center of the light quantity in the incident direction of the light beam L5a imaged on the wafer 22 (in other words, the principal ray of the light beam L5a)
(A non-telecentric state). That is, the position of the image may be laterally shifted in the wafer plane due to the slight shift (defocus) of the wafer 22 in the optical axis AX direction. In the present invention, in order to prevent this image shift, the angle of incidence of the illumination light beam on the reticle is adjusted by the reflection mirror 9 located at a position substantially conjugate with the reticle 18.
It is configured to change according to. Therefore, a certain incident angle ψ
After the illumination with the incident light beam L5a is performed for a fixed exposure amount, the reflecting mirror 9 is moved or the like, so that the illumination light beam L5b incident at the incident angle −ψ has the same exposure amount as described above. . As a result, the lateral shift of the center of gravity of the amount of light incident on the wafer with respect to the normal to the wafer surface is canceled out by the exposure at the incident angle + ψ and the exposure at the incident angle -ψ, and becomes zero.

In the projection type exposure apparatus according to the present embodiment, the light amount measuring device 25 for measuring the light amount irradiated on the reticle 18
Is provided, it is easy to realize that the exposure amount at the above incident angle + ψ and the exposure amount at the incident angle -ψ are constant and the same value. In addition, even when the exposure time is controlled instead of providing the light amount measuring device, each exposure amount can be similarly set to the same value.

Next, the reason why the depth of focus is increased by the present invention will be described. In FIG. 3, the reticle 18
When the wafer 22 is located at the image forming position of the upper circuit pattern 19 by the projection optical system 20, the optical path length connecting one point of the circuit pattern 19 and the corresponding one point on the wafer 22 depends on which part of the projection optical system 20. The rays that pass are equal. However, when the wafer 22 is shifted from the image forming position in the optical axis direction (that is, when the wafer 22 is defocused), the above-described optical path length becomes
It changes according to the passing position of the light beam in the projection optical system, especially the position in the pupil plane 21. At this time, the change amount δ of the optical path length
Is represented by δ = r ² Δf / 2, where r is the distance from the optical axis AX of the light passing position to the optical axis AX with respect to the light passing through the optical axis AX of the projection optical system 20. Δf is the amount of deviation from the imaging position of the wafer 22 in the optical axis direction.

Therefore, the circuit pattern 1 on the reticle 18
9 passes through the pupil plane 21 of the projection optical system 20 (that is, the optical path difference δ corresponding to the position r from the optical axis), that is, the phase difference exp (2πiδ / λ). To reach the wafer 22. This phase difference is a cause of the deterioration of the transfer image quality on the wafer 22 due to the defocus,
Generally, this is an amount called wavefront aberration due to defocus. In the present invention, since the illumination light beam to the reticle is made incident at an angle to the optical axis, the zero-order diffracted light Do
And the + 1st-order diffracted light Dp can pass through the pupil plane 21 at a position substantially equidistant from the optical axis AX. Therefore,
The phase of the 0th-order diffracted light Do and the phase of the + 1st-order diffracted light Dp are substantially equal, and the deterioration of the image quality due to defocus is extremely reduced. That is, a deep depth of focus can be obtained. In order to maximize the effect of increasing the depth of focus, the pupil plane 2
The optical axis AX of the 0th-order diffracted light Do and the + 1st-order diffracted light Dp on 1
That is, the incident angle の of the illuminating light beam may be determined so that the distance from the light source becomes exactly equal.

FIG. 2 is a diagram showing the configuration of a modification of the projection type exposure apparatus according to the first embodiment of the present invention. However, the configuration on the light source side from the fly-eye lens 6 and the configuration on the reticle side from the Fourier transform plane (pupil plane of the illumination optical system) 12 are the same as in the first embodiment shown in FIG. .
The light beam emitted from the fly-eye lens 6 is applied via a lens system 8 to a lens system 9a having a positive power and a lens system 9b having a negative power. The lens system 9a and the lens system 9b are arranged near a plane conjugate with the reticle 18. The sum of the powers of the lens systems 9a and 9b is 0. The lens systems 9a and 9b are movable in a plane perpendicular to the optical axis AX by lens driving members 10c and 10d, respectively. The luminous flux transmitted through the lens systems 9a and 9b movable by the driving members 10c and 10d becomes a luminous flux having a principal ray different from the optical axis AX of the illumination optical system, and a position different from the optical axis AX on the Fourier transform surface 12. Focus on The reticle side from the Fourier transform surface 12 is the first
This is the same as the embodiment.

In FIG. 2, the lens systems 9a and 9b are moved in opposite directions with respect to the optical axis and at substantially equal distances. As a result, the luminous flux transmitted through the lens systems 9a and 9b becomes
The light enters the lens system 11 at a specific angle with respect to the optical axis AX. If the positions of the lens systems 9a and 9b are changed by the lens driving members 10c and 10d, the emitted light beam can be directed to an arbitrary direction. The lens driving members 10c and 10d are controlled by the control circuit 26.

Further, a new lens system having a positive power is provided on the reticle 18 side from the lens system 9b, and this lens system is made movable by a lens driving member. Further, the lens systems 9a and 9b are newly added. A configuration may be adopted in which the sum of the powers of the lens system having the positive power and the power of the lens system having the positive power becomes zero. Similarly, a lens system having negative power is provided on the light source side with respect to the lens system 9a, and the total power of the lens systems 9a and 9b and the newly added negative power lens system becomes zero. Is also good. Note that the configuration of the lens system whose position is variable is not limited to the above combination, but is a lens group including a plurality of lens elements having a total power of each lens of 0. Any configuration may be used as long as the illumination light beam can be directed to an arbitrary direction by moving the element. Further, the lens element to be driven is not specified, but may be any lens element capable of directing the illumination light beam in an arbitrary direction.

FIG. 5 is a diagram showing a schematic configuration of a projection type exposure apparatus according to a second embodiment of the present invention. However, the light source side from the fly-eye lens 6 and the reticle 18 side from the lens system 13 are omitted for simplicity, as in the first embodiment. When the reticle 18 is used as the object plane, the broken line portion is the pupil plane 12, that is, the Fourier transform plane of the reticle 18. The pupil plane 12 and the exit-side surface of the fly-eye lens 6 are connected by a light transmitting means such as an optical fiber 9c. Therefore, the exit side surface of the fly-eye lens 6 corresponds to the pupil plane 12. The aperture stop 7 is a stop for determining the coherence factor σ of the illumination light beam as in the first embodiment.

The exit side of the optical fiber 9c, that is, the pupil plane 12
The side is movable by a driving member 10 e, so that the illumination light flux (light source image) can be distributed to an arbitrary position in the pupil plane 12. Further, the drive member 10e is controlled by the control circuit 26 as in the first embodiment. Next, the first
An exposure method using the exposure apparatus according to the embodiment will be described with reference to FIGS. 6 (a) and 6 (b).

FIGS. 6A and 6B are flowcharts showing an exposure method according to an embodiment of the present invention. The difference between FIG. 6A and FIG. 6B is whether or not to suspend the exposure when driving the reflecting mirror 9. Prior to the exposure, the shutter 5 is in a state of blocking the light beam L2.
Here, the number of times the position of the reflecting mirror 9 is changed, the coordinates of each reflecting mirror position, and the exposure amount for each coordinate are determined (step 10).
1). However, as described above, the so-called light amount center of gravity obtained by multiplying the angle of incidence of the light beam L5 corresponding to each position of the reflecting mirror 9 on the reticle 18 by each of the illumination light amounts illuminated at that position is averaged,
If the wafer 22 is displaced from the optical axis AX of the projection optical system 20 and the illumination optical system, there is a possibility that a transfer image may be laterally displaced due to minute defocus of the wafer 22. Therefore, it is necessary to determine each position of the reflecting mirror 9 and the amount of illumination light (exposure amount) to be illuminated so that the light amount center of gravity coincides with the optical axis AX. This means that one pattern exposure is completed by 2 m exposures (m is a natural number), and the coordinates of the reflecting mirror 9 are determined m times. In this case, the position may be set so as to be symmetrical with respect to the incident light beam and the optical axis AX in the case of the time. A method of determining the angular coordinates of each of the plurality of positions of the reflecting mirror 9 during the exposure operation will be described later.

Next, the drive member 10 is controlled by the control circuit 26.
An operation command is given to a and b, and the reflecting mirror 9 is set at a predetermined first position (step 102). The first position is input by an operator using an input device included in the control circuit 26. Alternatively, the information input by the operator using the input device may be information relating to the circuit pattern 19 on the reticle 18, and the control circuit 26 may determine the first position of the reflecting mirror 9 based on the information. Similarly, the necessary total exposure amount E is also input from the input device by the operator. The control circuit 26 may determine how much exposure is to be performed at each position of the reflecting mirror 9 or may be input by an operator.

Subsequently, the actual exposure operation starts. Reflector 9
Are substantially fixed at the first position determined above.
In this state, the control circuit 26 issues a "shutter open command" to the shutter drive unit 4, and the shutter 3 opens to start exposure (step 103).
8 is illuminated, so that the circuit pattern 19 is transferred onto the wafer 22. At this time, a part of the illumination light flux transmitted through the semi-transmissive mirror 16 is received by the light quantity measuring device 25 and is photoelectrically converted. The integrated value of the light amount signal S is a predetermined value, that is,
When the exposure amount corresponding to the previously determined first position is reached (step 104) or immediately before that, the control circuit 26
Issues an operation command to the driving members 10a and 10b,
Is changed to the previously determined second position (step 1).
05). When the integral value (integrated light amount) of the light amount signal S reaches a predetermined value as shown in FIG. 6B, the shutter 3 is closed once (step 105a), exposure is stopped, and then the reflecting mirror 9 is moved. Then, after the reflecting mirror 9 is almost fixed at a predetermined position, the shutter 3 is opened again (step 10).
5b) Exposure may be restarted.

When the integrated value of the light quantity signal S reaches a predetermined value at the second position of the reflecting mirror 9 (step 106),
Or, just before that, the reflecting mirror 9 is moved in the same manner as described above,
The third position is almost fixed, and the exposure is continued. At this time, the shutter 3 may be closed once to stop the exposure, as described above. Thereafter, exposure is performed in the same manner while changing the position of the reflecting mirror 9 to m positions. At the m-th position of the reflecting mirror 9, when the integrated value of the light amount signal S reaches the set total exposure amount E (step 107), the shutter 3 is closed to end the exposure.

Incidentally, the exposure amount at each position is represented by E ₁ , E ₂ ,.
_m (ΣE _i = E, 1 ≦ i ≦ m), the exposure to the first position ends when the integrated value of the light amount signal S reaches E ₁ or immediately before it, and Exposure to the position is terminated when the integrated value reaches E ₁ + E ₂ or immediately before. That is, among the exposures at the first to m-th positions, the exposure at an arbitrary n-th position is terminated when the integral value is ΔE _I (1 ≦ i ≦ n).
Is reached.

When the shutter 3 is closed once during the movement of the reflecting mirror 9 to suspend the exposure, the integral value is reset to 0 when the exposure is suspended. Then start the exposure again, the light amount integrated value of the signal S may also be called to terminate the exposure for any position of the n when it becomes a predetermined value E _n. The exposure according to the embodiment of the present invention is completed as described above. Thereafter, the wafer 22 is translated by the wafer stage 23 in a plane perpendicular to the optical axis AX, and another exposure is performed on another exposure area of the wafer 22. May go. Alternatively, the reticle 18 may be replaced, and another circuit pattern may be overlaid and exposed on the already exposed area. Note that wafer 2
In the case where a new exposure is performed at the other position 2, the position of the reflecting mirror 9 may be reversed from the m-th position to the first position and end at the first position.

In the above exposure method, when the reflecting mirror 9 is moved while the exposure is continued, illumination light from a direction other than a predetermined direction enters the reticle 18 while the reflecting mirror 9 is moving. Then, the effect of obtaining the above-described high resolution and a large depth of focus may be reduced. In order to prevent this, a spatial filter having a transmission portion only at a predetermined position may be provided near the pupil plane 12 between the lens systems 11 and 13 in FIG. In this spatial filter, positions that are equal to the positions on the pupil plane 12 of the illumination light beams L4a and L4b generated by the reflecting mirror 9 at each position are set as transmission portions, and the other positions are set as light shielding portions. Since the diameter of each transmission portion determines the σ value of each illumination light beam corresponding thereto, the diameter of the fly-eye lens 6 previously determined is optically equivalent to the aperture stop 7 at the exit side surface, that is, the fly-eye lens. 6 The diameter is determined in consideration of the magnification relationship between the exit side surface (conjugated to the pupil plane 12) and the pupil plane 12. Further, the diameter of the specific transmitting portion may be smaller than the equivalent diameter. That is, the σ value of a specific one of the light beams incident on the reticle 18 may be reduced.

The pupil plane 12 may be provided with a light scattering member such as a lemon skin filter. Dust, defects, and the like on the movable optical member can be blurred by the light scattering member, and uneven illuminance on the reticle 18 due to the dust, defects, and the like can be prevented. Note that the image forming relationship between the reticle 18 and the movable optical member (reflecting mirror 9) is blurred by the light scattering member, but does not adversely affect the effects of the present invention.

Next, a method of determining the rotational angle position of the reflecting mirror 9 will be described. In each embodiment of the present invention, the illuminating light beam L5 is irradiated on the reticle 18 and the reticle 18 at an angle inclined with respect to the optical axis AX. As described above, when the tilt angle of the illumination light beam L5 is adjusted such that the 0th-order diffracted light Do and the + 1st-order diffracted light Dp pass on the pupil plane 21 of the projection optical system 20 at a position substantially equidistant from the optical axis AX, the focal depth becomes Can be maximized. Therefore, to increase the depth of focus, 0
Angle between the first-order diffracted light Do and the + 1st-order diffracted light Dp, that is,
The incident direction of the illumination light beam L5 may be determined according to the pitch and direction of the circuit pattern 19 to be transferred. In order for the 0th-order diffracted light Do and the + 1st-order diffracted light Dp to be equidistant on the pupil plane 21 with respect to the optical axis AX, the illumination light beam L5 is
It is sufficient that the light is incident on a plane parallel to the direction vector of No. 9 and perpendicular to the reticle at an angle ψ given by sin ／ = λ / 2P.

FIG. 7A is a diagram showing an example of a circuit pattern on a reticle. This circuit pattern is a 1: 1 line and space pattern. FIG.
FIG. 7B is a diagram showing the circuit pattern shown in FIG. 7A in which the incident angle of the illumination light beam that maximizes the depth of focus on the reticle is replaced with a position on the pupil plane 12 of the illumination optical system. .
The sine of the angle of incidence of the illumination light beam on the reticle 18 is
Is converted to a position (a distance r from the optical axis AX).
The center position of the illumination light beam with respect to the line-and-space pattern (pitch P) in FIG.
If it is on α or Lβ, the depth of focus can be maximized. At this time, the line segments Lα and Lβ are sin
^It suffices that the optical axis AX is separated from the optical axis AX in the pattern pitch direction by α and β corresponding to an angle of ⁻¹ (λ / 2P) (angle incident on the reticle). That is, the position of the reflecting mirror 9 is shown in FIG.
When a line-and-space pattern as shown in (a) is transferred, the center (principal ray) of the illumination light beam L4a or L4b reflected by the reflecting mirror 9 is reflected on the pupil plane 12 by a line segment Lα, Alternatively, it is better to determine so as to coincide with Lβ.

FIG. 8A is a diagram showing another example of the circuit pattern. This circuit pattern has a pitch P in the horizontal direction.
x, and arranged at a pitch Py in the vertical direction. FIG. 8B
FIG. 9A is a diagram showing the circuit pattern shown in FIG. 8A in which the incident angle of the illumination light beam that maximizes the depth of focus on the reticle is replaced by a position on the pupil plane 12 of the illumination optical system. In this case, the center position of the illumination light beam that maximizes the depth of focus is four points on the pupil plane 12, Lγ, Lε, Lζ, and Lη. Therefore, the position of the reflecting mirror 9 may be any direction as long as the principal ray of the illumination light beam is directed to the four points Lγ, Lε, Lζ, and Lη on the pupil plane 12.

In FIG. 8, γ, ε, ζ, and η are distances given by γ = ε = λ / 2Pxζ = η = λ / 2Py, respectively. Even if the circuit pattern on the reticle has any other shape, similarly to the above, the illumination light flux such that the 0th-order diffracted light and the + 1st-order diffracted light pass the same distance from the optical axis on the pupil plane in the projection optical system. May be determined. When circuit patterns having a plurality of pitches are mixed on the reticle, the angle of incidence of the illumination light beam on the reticle may correspond to the optimum angle of each circuit pattern, or may be the average of each optimum angle. . Alternatively, the angle may be obtained by multiplying a weight according to the fineness of the pattern to obtain an average.

[0046]

As described above, according to the present invention, a reticle can be irradiated with a light beam at a predetermined incident angle. For this reason, 1 is generated from the reticle circuit pattern.
Even when the next-order diffracted light is generated in a direction at an angle larger than the numerical aperture of the projection optical system, an image of a circuit pattern can be formed, and the minimum pattern size that can be projected can be further reduced. Furthermore, since the 0th-order diffracted light and the 1st-order diffracted light are transmitted on the pupil plane of the projection optical system at positions substantially equidistant from the optical axis of the projection optical system, the depth of focus of the projected image can be increased.

Further, according to the present invention, even when a conventional reticle is used, the resolution is improved and the depth of focus is increased, which is almost the same as the case where the phase shift reticle is used. Moreover, the conventional reticle is much easier to manufacture and inspect than the phase shift reticle.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a modification of the projection exposure apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration from a Fourier transform surface of a reticle to a wafer of the projection type exposure apparatus according to the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration from a Fourier transform surface of a reticle to a wafer of a projection type exposure apparatus according to a conventional technique.

FIG. 5 is a diagram showing a schematic configuration of a projection exposure apparatus according to a second embodiment of the present invention.

FIGS. 6A and 6B are flowcharts showing an exposure method according to an embodiment of the present invention.

7A is a diagram illustrating an example of a circuit pattern on a reticle, and FIG. 7B is a diagram illustrating an incident angle of an illumination light beam that maximizes the depth of focus of the circuit pattern illustrated in FIG. FIG. 3 is a diagram showing the system replaced by positions on a pupil plane.

FIG. 8A is a diagram showing another example of a circuit pattern;
FIG. 2B is a diagram illustrating the circuit pattern illustrated in FIG. 1A, in which the incident angle of the illumination light flux that maximizes the depth of focus on the reticle is replaced with a position on a pupil plane of the illumination optical system.

[Explanation of symbols]

3 shutter, 4 shutter drive unit, 9 reflecting mirror,
9a, 9b: lens system, 9c: optical fiber, 10a,
10b: driving element, 10c, 10d: lens driving member,
10e: drive member, 26: control circuit.

Claims (33)

(57) [Claims] An illumination optical system for irradiating illumination light to a mask,
And a projection optical system that projects the illumination light onto the substrate, the exposure apparatus for transferring a pattern of the mask onto the substrate, the mask the illumination light from different directions at a predetermined angle of incidence
From the optical axis on the pupil plane of the illumination optical system so that
Intensity centers of the illumination light are respectively set at a plurality of eccentric positions.
A movable optical member to be set; and the illumination light when transferring the pattern onto the substrate.
Are switched to the plurality of positions, respectively.
And a driving member for driving the movable optical member . 2. The pupil plane of the illumination optical system, wherein the plurality of positions are
Above and away from the optical axis in the arrangement direction of the pattern
The exposure apparatus according to claim 1, the distance between the optical axis in accordance with the fineness of the pattern <br/> characterized Rukoto set to be substantially equal. 3. The pattern is arranged at a first pitch in a first direction.
When having a periodic structure, the plurality of positions are
The first direction from the optical axis on the pupil plane of the illumination optical system;
Parallel, separated by a distance corresponding to the first pitch
2. The method according to claim 1, wherein the first line segment is set on a pair of first line segments.
3. The exposure apparatus according to 1 or 2 . 4. The wavelength of the illumination light is λ, and the first pitch is
As P, the incident angle の of the illumination light is sinψ = λ / 2P
The distance between each of the first line segments and the optical axis is set so that
An apparatus according to claim 3, characterized in that the constant. 5. The method according to claim 1, wherein the pattern is a first direction orthogonal to the first direction.
With a periodic structure that is arranged at a second pitch in two directions
The plurality of positions are positioned on an optical axis on a pupil plane of the illumination optical system.
From the second pitch in the second direction.
And a pair of parallel second line segments separated by the same distance
The exposure apparatus according to claim 3, wherein the exposure apparatus is set at an intersection with the first line segment . 6. The pattern is arranged at a first pitch in a first direction.
Are arranged in a second direction orthogonal to the first direction.
When having a periodic structure arranged in
Is located on a pupil plane of the illumination optical system with respect to the first direction.
Away from the optical axis by a distance corresponding to the first pitch, and
The distance corresponding to the second pitch from the optical axis in the second direction.
Claim 1 or characterized in that it is set apart away
3. The exposure apparatus according to 2 . 7. The method according to claim 1, wherein the plurality of positions are changed according to a pattern to be transferred onto the substrate.
The exposure apparatus according to any one of claims 1 to 6 . 8. A light amount gravity center on a pupil plane of the illumination optical system is front.
The exposure apparatus according to any one of claim 1 to 7, characterized that you almost coincides with Kihikarijiku. Wherein said exposure according to any one of claims 1 to 8, characterized in that intensity center in each position, further comprising a detection means for detecting independently the light level of the illumination light set apparatus. 10. The illumination optical system is substantially arranged on a pupil plane.
And a spatial filter defining the numerical aperture of the illumination light is updated.
The method according to any one of claims 1 to 9, wherein
3. The exposure apparatus according to claim 1 . 11. The illumination light at each of the plurality of positions.
11. The method according to claim 1, wherein the light amounts are made substantially equal.
The exposure apparatus according to any one of the above . 12. Diffraction lights having different orders from each other generated from the pattern by irradiation of illumination light whose center of intensity is set at each of the positions are illuminated on a pupil plane of the projection optical system. In each of the above-mentioned strengths, passing through a position almost equidistant from the axis
The exposure apparatus according to any one of claim 1 to 11, characterized in that setting the heart. 13. Even if the substrate is displaced from the image forming position of the projection optical system, the two patterns of diffracted lights having different orders generated from the pattern by the irradiation of the illumination light whose intensity centers are set at the respective positions. The intensity centers are set so that their wavefront aberrations are substantially equal.
An apparatus according to any one of 12. 14. The method of claim 13, wherein the incident angle to the mask of the illumination <br/> light intensity center at each position is set [psi, of the illumination light two diffracted lights of the same order generated from the pattern by irradiation of _Assuming that the diffraction angle is θ and the numerical aperture of the projection optical system on the mask side is NAM, one of the two diffracted lights is sin (θ−
The exposure apparatus according to any one of claims 1 to 1 3, characterized in that [psi) ≦ NA _M the relationship is satisfied. 15. One of the diffracted lights that satisfies the above relationship is generated from the pattern with respect to the optical axis of the projection optical system.
Claims 1 to 4, characterized in that a substantially symmetrical order diffracted light
3. The exposure apparatus according to claim 1. 16. The wavelength of the illumination light is λ, and the wavelength of the illumination light is
The incident angle on the mask is ψ, and the mask of the projection optical system is
And the numerical aperture of the side and NA _M, can be transferred on the substrate
The minimum pitch of the pattern is λ / (NA _M + sinψ)
The method according to any one of claims 1 to 15, wherein
Exposure equipment . 17. The projection optical system, wherein the wavelength of the illumination light is λ,
The numerical aperture as NA _M of the mask side, the pattern
This has a smaller periodic structure than pitch lambda / NA _M is
The method according to any one of claims 1 to 16, wherein
Exposure equipment . 18. A numerical aperture of illumination light whose intensity center is set at each of the positions and a numerical aperture of the projection optical system on the mask side.
The exposure apparatus according to any one of claims 1 to 17 , wherein the ratio is set to about 0.2 to 0.3. 19. A method of irradiating a mask with illumination light through an illumination optical system, and applying the illumination light to a substrate through a projection optical system.
The method for exposing the mask , wherein the illumination light is irradiated from a different direction at a predetermined incident angle.
Movable optical member in the illumination optical system so that
Moved and decentered from the optical axis on the pupil plane of the illumination optical system
Switching the intensity center of the illumination light to a plurality of positions
And set the intensity center of the illumination light at each of the plurality of positions.
The exposure amount given to the substrate reaches a predetermined value.
Irradiating the mask with the illumination light at the point in time . 20. The pupil of the illumination optical system, wherein the plurality of positions are
Away from the optical axis on the surface in the arrangement direction of the pattern
The exposure method according to claim 19, the distance between the optical axis in accordance with the fineness of the pattern <br/> characterized Rukoto set to be substantially equal. 21. The pattern according to claim 1, wherein the pattern is formed at a first pitch in a first direction.
When having a periodic structure to be arranged, the plurality of positions are:
The first direction from the optical axis on the pupil plane of the illumination optical system;
Parallel with each other at a distance corresponding to the first pitch
A pair of first line segments.
Item 21. The exposure method according to Item 19 or 20 . 22. The wavelength of the illumination light is λ, the first pitch
Is P, the incident angle の of the illumination light is sinψ = λ / 2
The distance between each of the first line segments and the optical axis is set to be P.
The exposure method according to claim 21, wherein the setting is performed . 23. The pattern is orthogonal to the first direction.
Having a periodic structure arranged at a second pitch in the second direction
The plurality of positions are positioned on an optical axis on a pupil plane of the illumination optical system.
From the second pitch in the second direction.
And a pair of parallel second line segments separated by the same distance
23. The exposure method according to claim 21, wherein the exposure method is set at an intersection with the first line segment . 24. The method according to claim 17, wherein the pattern is formed at a first pitch in a first direction.
Arranged in a second direction orthogonal to the first direction.
When having a periodic structure arranged at a pitch, the plurality of
The position is on the pupil plane of the illumination optical system with respect to the first direction.
Away from the optical axis by a distance corresponding to the first pitch, and
According to the second pitch from the optical axis in the second direction
20. The wireless communication device according to claim 19, wherein the distance is set to be a distance.
Or the exposure method according to 20 . 25. The exposure method according to any one of claims 1 9-24, wherein the plurality of positions in accordance with the pattern to be transferred onto the substrate is changed. 26. A gravity center of a light amount on a pupil plane of the illumination optical system.
Claim 1 9 to substantially coincide to said Rukoto to the optical axis
The exposure method according to any one of items 25 . 27. Two diffracted lights having different orders generated from the pattern by the irradiation of illumination light whose intensity centers are set at the respective positions, on the pupil plane of the projection optical system. In each of the above-mentioned strengths, passing through a position almost equidistant from the axis
The exposure method according to any one of claims 1 9 to 26, characterized in that setting the heart. 28. Even when the substrate is displaced from the image forming position of the projection optical system, two diffracted lights having different orders from each other are generated from the pattern by irradiation of illumination light whose intensity centers are set at the respective positions. 10. The apparatus according to claim 19 , wherein the intensity centers are set so that the wavefront aberrations are substantially equal.
28. The exposure method according to any one of items 27 to 27 . 29. The angle of incidence to said mask illumination <br/> light intensity center at each position is set [psi, of the illumination light two diffracted lights of the same order generated from the pattern by irradiation of _Assuming that the diffraction angle is θ and the numerical aperture of the projection optical system on the mask side is NAM, one of the two diffracted lights is sin (θ−
The exposure method according to any one of claims 1 9 to 28, characterized in that [psi) consisting ≦ NA _M relationship is satisfied. 30. One of the diffracted lights that satisfies the above relation is generated from the pattern with respect to the optical axis of the projection optical system.
Claim 29, characterized in that a substantially symmetrical order diffracted light
3. The exposure apparatus according to claim 1. 31. The wavelength of the illumination light is λ, and the wavelength of the illumination light is
The incident angle on the mask is ψ, and the mask of the projection optical system is
And the numerical aperture of the side and NA _M, can be transferred on the substrate
The minimum pitch of the pattern is λ / (NA _M + sinψ)
The exposure method according to any one of claims 19 to 30, wherein: 32. The wavelength of said illumination light is λ, said projection optical system
The numerical aperture as NA _M of the mask side, the pattern
This has a smaller periodic structure than pitch lambda / NA _M is
The exposure method according to any one of claims 19 to 31, wherein: 33. The numerical aperture of illumination light whose intensity center is set at each of the positions and the numerical aperture of the projection optical system on the mask side.
The exposure method according to any one of claims 19 to 32 , wherein the ratio is set to about 0.2 to 0.3.